Massage beds are used in physiotherapy clinics, hospitals, beauty shops, and spa resorts. As people become increasingly health conscious, more and more massage beds are required.
A typical massage bed includes multiple internal massage units each having a motor mounted therein. A shaft of the motor is connected to an eccentric wheel. When the motor is turned on, the shaft rotates the eccentric wheel. The rotating eccentric wheel contacts a surface of the massage bed to produce vibrations to massage corresponding body parts.
The above motor employs a rolling bearing to support the shaft. Referring to FIG. 1, when a rolling bearing 100 is assembled in a bearing hub or bearing mounting portion 310 at an end of a motor housing 300, a radial gap is formed between an inner diameter of the mounting portion 310 and an outer diameter of the rolling bearing 100. This gap is filled with glue to rigidly fix the bearing to the bearing mounting portion. However, over time the vibration and heat will cause the glue to crack of otherwise release the bearing leading to failure of the motor. Alternatively, a larger gap may be provided which is filled with a rubber sleeve or rubber bushing. However, this method is not reliable. Experiments indicate that, after the motor runs for 200 hours, the rubber bushing becomes loose and fails due to the radial eccentric alternating load produced during operation of the massage bed, leading to failure of the motor.